U.S. patent application number 12/617059 was filed with the patent office on 2010-07-22 for screw locking systems for bone plates.
Invention is credited to Javier E. Castaneda, Jorge L. Orbay.
Application Number | 20100185246 12/617059 |
Document ID | / |
Family ID | 36602197 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100185246 |
Kind Code |
A1 |
Castaneda; Javier E. ; et
al. |
July 22, 2010 |
Screw Locking Systems for Bone Plates
Abstract
Bone screws have heads which are provided with a hex socket as
well as a threaded portion. A screw driver system includes a hex
driver and a threaded driver. The screw driver system permits
driving the screw through a plate system into a bone until desired
compression is obtained. Then the screw is locked to the plate
while maintaining the imparted compression.
Inventors: |
Castaneda; Javier E.;
(Miami, FL) ; Orbay; Jorge L.; (Miami,
FL) |
Correspondence
Address: |
GORDON & JACOBSON, P.C.
60 LONG RIDGE ROAD, SUITE 407
STAMFORD
CT
06902
US
|
Family ID: |
36602197 |
Appl. No.: |
12/617059 |
Filed: |
November 12, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11017313 |
Dec 20, 2004 |
|
|
|
12617059 |
|
|
|
|
Current U.S.
Class: |
606/305 ;
606/104; 606/281 |
Current CPC
Class: |
A61B 17/8875 20130101;
A61B 17/861 20130101; A61B 17/8057 20130101 |
Class at
Publication: |
606/305 ;
606/281; 606/104 |
International
Class: |
A61B 17/88 20060101
A61B017/88; A61B 17/86 20060101 A61B017/86; A61B 17/56 20060101
A61B017/56 |
Claims
1.-28. (canceled)
29. A method for attaching a plate to a bone with a screw through a
hole in the plate, said method comprising: attaching the screw to a
driver; inserting the screw through the hole in the plate; driving
the screw into a bone while biasing the plate against the bone with
the driver but not the screw; and releasing the screw from the
driver while locking it to the plate.
30. A bone plating system for stabilizing bone, comprising: a bone
screw having, a threaded shank having a first end, a second end,
and an overall diameter; and a screw head having a portion of
larger diameter than said overall diameter, said screw head
defining a threaded first driver engagement means for engaging a
first driver for the screw and a non-threaded second driver
engagement means for engaging a second driver for the screw, said
threaded first driver engagement means located radially outward of
said non-threaded second driver engagement means; a screw driver
system having, a first driver having an elongate body having a
first end and a second end with a throughbore extending through
said body from said first end to said second end and having first
screw engagement means located at said second end for engaging said
threaded first driver engagement means, and a second driver having
an elongate body having a first end and a second end and
dimensioned to fit through said throughbore of said first driver,
and having said second screw engagement means located at said
second end of said second driver for engaging said second driver
engagement means; and a bone plate having, at least one screw hole
adapted to receive said screw and lockingly engage said screw head,
said first screw engagement means having a diameter exceeding a
diameter of said at least one screw hole, wherein said second
driver is adapted to rotate said bone screw into bone with
compression developed between said threaded shank of said bone
screw and said second end of said first driver, and once sufficient
compression is developed, said first driver is adapted to rotate
said screw head of said bone screw into engagement with said at
least one screw hole in said bone plate.
31. The system according to claim 30, wherein: said first driver
engagement means includes threads located inside said screw
head.
32. The system according to claim 31, wherein: said second driver
engagement means includes a socket portion of said screw head.
33. The system according to claim 30, wherein: said screw hole is
tapered.
34. The system according to claim 30, wherein: said plate has a top
and a bottom and said screw hole is threaded from said top to a
location between said top and bottom.
35. The system according to claim 30, wherein: said first and
second drivers are releasably lockable to each other.
36. The system according to claim 30, wherein: said first screw
engagement means is threads and said second screw engagement means
is a hex driver.
37. The system according to claim 36, wherein: said threads are
internal to said first driver.
38. The system according to claim 36, wherein: said threads are
external to said first driver.
39. The system according to claim 30, wherein: said bone plate
comprises metal.
40. The system according to claim 30, wherein: said screw head is
frustroconical along an exterior surface that axially extends
coextensively with said first and second driver engagement
means.
41. The system according to claim 30, wherein: said screw head is
cylindrical.
42. The system according to claim 41, wherein: said screw head
includes an exterior having a length, and said screw includes
helical threads abut an entirety of said length of said
exterior.
43. The system according to claim 30, wherein: said screw head has
a pair of external axially spaced apart non-helical circumferential
ridges structured for engagement with the inner surface of the
screw hole in the bone plate, wherein upon insertion of the screw
head into the screw hole said circumferential ridges provide
engagement with said screw hole.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates broadly to orthopedic devices. More
particularly, this invention relates to systems for locking bone
screws relative to bone plates.
[0003] 2. State of the Art
[0004] For various fractures of bones of the body, plating is a
well known technique to impart the stabilization desirable for
proper healing. In plating, a rigid, typically metal plate is
placed on the outer surface of the bone across the fracture, and
screws are secured through the plate and into the bone on either
side of the fracture in a manner which permits the rigid plate to
offer support to the bone during healing.
[0005] The screws include threads along a shaft adapted to engage
cortical bone. Most commonly, the head portion of the screw is
generally a standard screw head which provides a compressive force
about a corresponding round screw hole of the plate as the screw is
thread into the bone, thereby causing compression of the plate
against the bone.
[0006] U.S. Pat. No. Re. 28,841 to Allgower describes a plate that
is used with generally standard screws having heads with a convex
undersurface. The plate includes oblong screw holes which each
define at one end an upper ramped portion and a generally smaller
radius of curvature about the ramped portion. In use, a hole is
drilled into the bone through the screw hole adjacent the ramp and
a screw is inserted through the screw hole adjacent the ramp into
the drilled hole and rotated until the head of the screw contacts
the ramp. Upon such engagement, there is displacement of the bone
plate in a direction to move the ramped portion away from the screw
and the cause the plate to apply pressure to maintain the bone
parts together about the fracture in tight engagement.
[0007] More recently, particularly at the metaphysis of long bones
though not limited thereto, there have been desirable results with
screws having exteriorly threaded heads which threadably engage
threads in the plate to lock the screws relative to the plate and
thereby limit compression of the plate relative to the bone.
However, such systems do not provide the necessary control of
compression between the plate and bone. Control over compressive
forces is lost as soon as the threads of the head of the screw lock
relative to the plate. Therefore, such a system provides
sub-optimal stability.
[0008] Certain plates sold by Synthes are designed with a hole
called a COMBI-HOLE.TM.. The COMBI-HOLE.TM. is an elongated screw
hole including two joined circular sections, each extending through
approximately 250.degree.. One of the circular sections is threaded
and thus adapted to received a screw with a threaded head at a
fixed angle. When used as such, the system has the same lack of
control over compression as discussed above.
SUMMARY OF THE INVENTION
[0009] It is therefore an object of the invention to provide a
plate and screw system whereby the amount of compression between
the plate and bone can be controlled completely by the surgeon.
[0010] It is an additional object of the invention to provide a
plate and screw system which permits complete control over
compression prior to and during locking the screw to the plate.
[0011] In accord with these objects, which will be discussed in
detail below, bone screws according to the invention have heads
which are provided with a hex socket as well as a threaded portion.
A screw driver system according to the invention includes a hex
driver and a threaded driver. The threaded driver is provided with
an axial through bore which is dimensioned to receive the hex
driver. The screw driver system is coupled to a screw by threadably
engaging the threaded driver with the threaded portion of the screw
head, and delivering the hex driver through the bore in the
threaded driver to engage the hex socket in the screw head.
Optionally, a set screw is used to secure the hex driver to the
threaded driver. The end of the threaded driver is dimensioned to
have a diameter larger than the diameter of the head of the screw
with which it is used. According to a first embodiment, the screw
head is frustroconical with a smooth side surface and the screw
head includes internal threads coaxial with the hex socket. The
first embodiment is used with a bone plate having a frustroconical
screw hole.
[0012] When the screw is attached to the driver system and is
passed through the hole in the bone plate, the threaded driver
alone is used (or both drivers coupled together are used) to rotate
the screw to engage the bone. After the screw is advanced into the
bone, the frustroconical screw head enters the frustroconical screw
hole in the bone plate, but is prevented by the threaded driver
from contacting the inner wall of the screw hole. The larger
diameter end of the threaded driver prevents the screw head from
advancing further. Moreover, the end of the threaded driver
contacts the area of the bone plate surrounding the screw hole and
exerts compression on the plate as the screw is further advanced
into the bone. When the desired compression is reached, turning of
the threaded driver is stopped (and if the drivers where engaged,
they are now disengaged) and the hex driver is used to further
advance the screw. Turning the hex driver while holding the
threaded driver advances the screw while starting to decouple the
threaded portion of the screw head from the threaded driver. In
order to maintain compression until the screw head is locked in the
screw hole of the bone plate, the length of the threads on the
screw head and the threaded driver prevent the screw head from
being decoupled before the screw head is locked. When the
frustroconical screw head lockingly engages the frustroconical
screw hole, the threaded driver is backed off the screw head by
turning it in the direction opposite to driving.
[0013] A second embodiment of a bone screw according to the
invention is identical to the first embodiment but has a threaded
exterior surface on the wall of the frustroconical head. The
threaded surface creates high localized pressure between the thread
crests and the tapered screw hole wall of the plate. It also causes
some scoring and a better mechanical hold.
[0014] A third embodiment of a bone screw has a cylindrical head
with two unequal diameter circumferential edges, one near the top
and one near the bottom of the head, that make simultaneous contact
with the tapered screw hole wall of the plate when the head is
locked to the plate.
[0015] A fourth embodiment of a bone screw has a cylindrical head
with external threads and an internal hex socket. This embodiment
of the screw is used with the second embodiment of the threaded
driver which has internal threads which engage the exterior of the
screw head and is also used with a bone plate that has a
cylindrical threaded screw hole. The threads on the head of the
screw preferably advance at a similar rate to the threads on the
shaft so as to maintain the compression achieved while the head is
being locked to the plate. Alternatively, the pitch of the screw
head threads may be decreased slightly with respect to the screw
shaft threads so as to increase compression slightly as the screw
is locked to the plate.
[0016] Additional objects and advantages of the invention will
become apparent to those skilled in the art upon reference to the
detailed description taken in conjunction with the provided
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a side elevational view of a hex screw driver
according to the invention;
[0018] FIG. 2 is a transparent side elevational view of a threaded
screw driver according to the invention;
[0019] FIG. 3 is a transparent side elevational view of the hex
screw driver coaxially inserted through the threaded screw
driver;
[0020] FIG. 4 is a longitudinal sectional view of a first
embodiment of a bone screw according to the invention;
[0021] FIG. 5 is a partially transparent side elevational view of
the screw drivers of FIGS. 1 and 2 coupled to the screw of FIG.
4;
[0022] FIG. 6 is a broken partially transparent side elevational
view of the screw drivers and screw of FIGS. 1-5 and a bone plate
showing the screw unlocked from the plate during plate
compression;
[0023] FIG. 7 is a view similar to FIG. 6 but showing the screw
locked to the plate;
[0024] FIG. 8 is a view similar to FIG. 6 but showing a second
embodiment of a screw according to the invention;
[0025] FIG. 9 is a view similar to FIG. 7 but showing the second
embodiment of the screw;
[0026] FIG. 10 is a view similar to FIG. 8 but showing a second
embodiment of a threaded screw driver according to the invention
and a bone plate having a threaded screw hole;
[0027] FIG. 11 is a view similar to FIG. 9 but showing the second
embodiment of a threaded screw driver and the bone plate having a
threaded screw hole;
[0028] FIG. 12 is a view similar to FIG. 8 but showing another
embodiment of a bone screw according to the invention; and
[0029] FIG. 13 is a view similar to FIG. 9 but showing another
embodiment of a bone screw according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Turning now to FIGS. 1-3 a first embodiment of a screw
driver system 10 according to the invention includes a hex driver
12 and a threaded driver 14. The hex driver 12 includes a
cylindrical handle 16, a smaller diameter shank 18, and a male hex
end 20. The threaded driver 14 includes a cylindrical handle 22
with a tapered end 24. An exteriorly threaded cylinder 26 extends
from the tapered end 24. An axial through bore 28 extends through
the handle 22 and through the cylinder 26. The through bore 28
exhibits a tapered wall 30 just prior to the cylinder 26.
Optionally, a set screw hole 32 is arranged orthogonal to the bore
28. The hex driver 12 is dimensioned to fit through the bore 28 as
shown in FIG. 3 with the male hex end 20 extending beyond the
threaded cylinder 26. The tapered wall 30 in the bore 28 prevents
the hex driver 12 from passing through the bore. The screw driver
system 10 is designed for use with a bone screw of the type shown
in FIG. 4.
[0031] Turning now to FIG. 4, a bone screw 40 includes a threaded
shaft 42 having a cutting flute 44 at one end and a screw head 46
at the other end. The head 46 is substantially frustroconical and
houses a hex socket 48 and a threaded inner wall 50 which is
coaxial with the hex socket. Referring now to FIGS. 3-5, those
skilled in the art will appreciate that, when assembled, the
threaded cylinder 26 of the driver 14 engages the threaded inner
wall 50 of the screw head 46 and the male hex end 20 of the driver
12 engages the hex socket 48. The screw and driver assembly is
shown in FIG. 5. When the screw and drivers are assembled as shown,
the screw is ready to be inserted through a bone plate and threaded
into bone.
[0032] FIGS. 6 and 7 show two stages of applying the screw 40 to a
bone plate 50 having a frustroconical screw hole 52. After the
screw and drivers are assembled as shown in FIG. 5 and the drivers
are optionally fastened to each other with a set screw 34 through
the set screw hole 32, the handle 22 of the driver 14 is turned
while the screw 40 is inserted through the plate 50 and into a
pre-drilled hole in the bone (not shown). As the screw advances
into the bone, the head 46 of the screw advances toward the plate
50 and ultimately enters the frustroconical hole 52 as shown in
FIG. 6. Before the head 46 can frictionally engage the hole 53, the
tapered end 24 of the driver 14 abuts the plate 50. Since the head
46 of the screw 40 is threadably coupled to the end of the driver
14, it is prevented from advancing away from the driver 14 into the
hole 52. When the screw, driver and plate are arranged as shown in
FIG. 6, rotating the driver 14 advances the screw into the bone
while the tapered end 24 of the driver 14 compresses the plate 50
against the bone. When the surgeon feels that the proper amount of
compression has been achieved, rotation of the driver 14 is
stopped. If necessary, the set screw is 34 released from the hole
32 (FIG. 5) and the hex driver 12 is rotated further in the same
direction while the threaded driver 14 is held stationary. This
causes the screw 40 to advance while the head 46 rotates out of
engagement with the driver 14 until the head 46 frictionally
engages the hole 52 as shown in FIG. 7. The driver 12 may then be
removed by lifting it out of the socket in the screw head and the
bore in the driver 14. The driver 14, if not decoupled from the
screw by the advancement, can then be uncoupled by reverse
rotation.
[0033] From the foregoing, those skilled in the art will appreciate
that the system of the invention allows the surgeon to carefully
apply a controlled amount of compression to the plate prior to
locking the screw to the plate. It also maintains the selected
compression while the screw is being locked to the plate. The
tapered end of the threaded driver serves two functions, it reduces
friction between the driver and the plate, making it easier to
rotate the driver under compression. It also provides a clearer
view of the screw and screw hole during insertion of the screw into
the hole. However, it is not necessary that the driver be
tapered.
[0034] FIGS. 8 and 9 illustrate an alternate embodiment of a screw
140 which is substantially identical to the screw 40 having a
threaded shaft 142, a cutting flute at one end (not shown) and a
frustroconical head 146 at the other end. The difference between
this screw 140 and the screw 40 is that the outer surface of the
head 146 is threaded. The screw 140 works with the same driver
assembly 10 and bone plate 50 as the screw 40 in the same manner as
described above but the threaded surface 146 creates high localized
pressure between the thread crests and the tapered screw hole wall
52 of the plate. It also causes some scoring and a better
mechanical hold. The pitch of the threads 146 should be the same as
the pitch of the threads 142 to help maintain the same level of
compression and create one scoring track.
[0035] FIGS. 10 and 11 illustrate another embodiment of a bone
screw according to the invention. The screw 340 has a threaded
shaft 342 and a cylindrical head 346 with two unequal diameter
circumferential edges 346a, 346b. The interior of the head 346 is
the same as the head 46 of the screw 40 (FIG. 4) and the screw is
used with the driver assembly 10 (FIG. 3) and the bone plate 50
described above. When the screw 340 is locked into the tapered hole
52 as shown in FIG. 13, the two circumferential edges 346a, 346b
make simultaneous contact with the tapered hole, one near the top
and one near the bottom. Such circumferential ridges can also be
used on screws with frustroconical heads or any shaped head which
will rotate within the screw hole.
[0036] FIGS. 12 and 13 illustrate another embodiment of a bone
screw 240, a second embodiment of a bone plate 150, and a second
embodiment of a driver system 110. The driver system 110 uses the
same hex driver 12 as the driver system 10 but uses a different
threaded driver 114. The driver 114 has an interiorly threaded
cylindrical recess inside its tapered end 124 as opposed to the
exteriorly threaded cylinder 26 of the driver 14 (FIGS. 2 and 3).
The screw 240 has a cylindrical head 246 which is provided with
threads that match the threads in the recess 126 of the driver 114.
The screw head 246 also has an interior hex socket like the hex
socket 48 in the screw 40 (FIG. 4) but it does not have interior
threads like the threads 50 in the screw 40. The threads on the
shank 242 of the screw 240 have generally the same pitch as the
threads on the head 246. The plate 150 has a screw hole 152 with
interior threads which match the threads of the screw head 126. As
can be seen in FIGS. 10 and 11, the threads 152 terminate before
reaching the bottom of the plate 150. The screw, driver, and plate
of this arrangement operate in a manner similar to the systems
described above. The screw 240 is attached to the driver 114 by
threading its head 246 into the threaded recess 126 of the driver.
The driver 114 drives the screw into the bone and advances the head
246 to the top of the plate 150, but prevents it from entering the
threaded hole 152. The tapered end 124 of the driver abuts the top
of the plate and compresses it. When the surgeon feels the
appropriate amount of compression, the hex driver 12 is rotated
while keeping the threaded driver 114 stationary. This rotates the
screw head 246 out of engagement with the threaded recess 126 and
into engagement with the threaded hole 152. The screw head bottoms
out on the threads in the hole 152 before passing through the plate
150. It is desirable that multiple thread starts be provided on the
screw head 246 to avoid compression when the plate threads start to
engage and to avoid cross-threading. It is important to note that
the external threads on the head 246 are free to engage both the
driver and the plate and are not blocked from engaging either by
any other part of the head.
[0037] There have been described and illustrated herein embodiments
of a bone plating system and methods of using the same. While
particular embodiments of the invention have been described, it is
not intended that the invention be limited thereto, as it is
intended that the invention be as broad in scope as the art will
allow and that the specification be read likewise. For example,
while the screws have been described as having a hex socket which
is driven by a hex driver, it will be appreciated that other types
of sockets and drivers can obtain substantially the same results as
a hex socket and driver. It will therefore be appreciated by those
skilled in the art that yet other modifications could be made to
the provided invention without deviating from its scope as
claimed.
* * * * *